Research on the influence of segmented surface pretreatment of rolls on the interfacial bonding and crack inhibition of Ni60A repair layer by laser cladding

During the operation of large roll shafts, critical components experience severe wear and fatigue spalling under extreme thermal and mechanical loading conditions. This study systematically investigates the effects of different substrate surface pretreatment methods on the performance of laser cladding repair layers. The results demonstrate that preheating pretreatment effectively reduces thermal gradients during cladding, thereby lowering crack sensitivity. This approach achieved a reduced dilution rate of 21.91 % and enhanced shear strength by 11 %. EBSD analysis revealed that preheating promoted a homogeneous microstructure with well-developed cellular dendrites and equiaxed crystals, while oxidized specimens exhibited discontinuous grain boundaries and impurity-induced defects. Surface pretreatment with V-groove structures significantly improved interfacial bonding characteristics. With increasing groove depth, the wetting angle decreased by 19.8 %, while Ni element diffusion expanded by up to 112.77 %, collectively contributing to an 80 % improvement in shear strength. Microstructural analysis confirmed that the deep V-groove (350 μm) promoted uniform grain distribution, increased high-angle grain boundaries, and enhanced dislocation pinning. The Ni60A cladding layer exhibited a 9 % higher average hardness than the substrate, with an anomalously hardened interface zone attributed to grain refinement and high dislocation density. Fractographic analysis revealed that failure primarily occurs at the heat-affected zone interface, exhibiting typical ductile fracture morphology. Numerical simulations corroborated experimental findings, confirming that both preheating and V-groove pretreatment effectively reduce thermal gradients and minimize interfacial stress concentrations. This investigation provides valuable theoretical guidance for optimizing laser cladding repair processes and enhancing the mechanical performance of cladding layers in heavy industrial applications.